LEESBURG, Va. -- Comedian Stephen Colbert addressed House Democrats at their retreat here Friday, adding a bit of humor to an agenda dominated by big political fights on Capitol Hill.

Donning his character as a bombastic right-wing pundit, Colbert gave formal remarks and then let his character slip while he was interviewed by Minority Leader Nancy Pelosi. The event ended with a duet of the National Anthem with Colbert and Democratic Caucus Vice Chairman Joseph Crowley of New York.

"Republicans' loss in November has them soul searching ... whether or not they have souls,” Colbert cracked, according to notes taken by a person in the room.

He described himself and Pelosi as “frenemies” and vowed his sister would win a congressional seat in South Carolina.

“She’s tough as nails,” Colbert said, adding that he would like to interview her on his trademark “Better Know a District” segments.

“I have a few questions for her from her eighth-grade diary,” he said.

Regarding that interview series, Colbert said he thought Rep. Lynn Westmoreland, R-Ga., was the only lawmaker who had truly embarrassed himself in the zany interviews. Westmoreland “set himself on fire” when he remembered only three of the Ten Commandments he was trying to mandate public placement of,” Colbert said.